Reducer for electric vehicle

ABSTRACT

A reducer for an electric vehicle includes an input shaft connected to a motor, a differential disposed coaxially with the input shaft and relatively rotatable, a planetary gear train configured to decelerate power of the input shaft and transmit the power to a differential casing of the differential, and a drive shaft configured to penetrate the input shaft and coupled to one side gear of the differential.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Korean Patent Application No.10-2021-0095019, filed Jul. 20, 2021, the entire contents of which isincorporated herein for all purposes by this reference.

BACKGROUND Field

The present disclosure relates to a technology related to a structure ofa reducer for an electric vehicle.

Description of the Related Art

An electric vehicle operates a driving wheel with power of a motor thatoperates with electric power. A reducer or the like is disposed betweenthe motor and the driving wheel to provide the driving wheel with thepower of the motor after reducing the speed to an appropriate speed.

The reducer used for the electric vehicle needs to have a simple,compact configuration, if possible, have improved vehicle mountability,and implement a sufficient reduction ratio.

The foregoing explained as the background of the disclosure is intendedmerely to aid in the understanding of the background of the presentdisclosure, and is not intended to mean that the present disclosurefalls within the purview of the related art that is already known tothose skilled in the art.

SUMMARY

The present disclosure is proposed to solve these problems and aims toprovide a reducer for an electric vehicle, having a simple, compactconfiguration, a relatively short overall length, and improved vehiclemountability, reduces a weight and costs, ensures improved assemblyproperties and maintainability, and implements improved durability.

An exemplary embodiment of the present disclosure provides a reducer foran electric vehicle, the reducer including an input shaft connected to amotor, a differential disposed coaxially with the input shaft andinstalled to be relatively rotatable, a planetary gear train configuredto decelerate power of the input shaft and transmit the power to adifferential casing of the differential, and a drive shaft configured topenetrate the input shaft and coupled to one side gear of thedifferential.

The planetary gear train may include a sun gear provided on the inputshaft, a carrier engaging with the differential casing, and a ring gearfixed to a casing.

Planetary pinions rotatably supported on the carrier may include a firststage pinion engaging with the sun gear, and a second stage pinionengaging with the ring gear, and the first stage pinion may have alarger diameter than the second stage pinion.

The carrier and the differential casing may engage with each other by aspline by sliding in an axial direction.

An end of the input shaft may be inserted into the differential casing,and a first bearing may be installed between an inner circumferentialsurface of the differential casing and an outer circumferential surfaceof the input shaft.

The input shaft may be supported on the casing by a second bearing and athird bearing disposed to be spaced apart from each other in an axialdirection, and the differential casing may be supported by a fourthbearing on the casing at a position spaced apart from the first bearingin the axial direction.

An oil supply part may be provided in the casing to supply oil through aspace between the input shaft and the drive shaft, and the oil supplypart may be formed to supply the oil to a gap between the end of theinput shaft and the drive shaft.

A parking gear may be provided on the carrier.

A spline may be formed between an outer circumferential surface of thecarrier and an inner circumferential surface of the parking gear so thatthe parking gear is coupled to the outer circumferential surface of thecarrier by sliding in an axial direction.

A pin insertion port for fixing a pinion shaft may be provided in thedifferential casing and opened toward the carrier of the planetary geartrain.

The present disclosure may provide the reducer for an electric vehicle,which has a simple, compact configuration, a relatively short overalllength, and excellent vehicle mountability, reduces a weight and costs,ensures excellent assembly properties and maintainability, andimplements excellent durability.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a view illustrating a first embodiment of a reducer for anelectric vehicle according to the present disclosure.

FIG. 2 is a structural view briefly illustrating a structure illustratedin FIG. 1 .

FIG. 3 is a view illustrating a second embodiment made by adding aparking gear to a configuration illustrated in FIG. 1 .

FIG. 4 is a view illustrating a third embodiment of the reducer for anelectric vehicle according to the present disclosure.

FIG. 5 is a view illustrating a fourth embodiment of the reducer for anelectric vehicle according to the present disclosure.

FIG. 6 is a view illustrating a fifth embodiment of the reducer for anelectric vehicle according to the present disclosure.

DETAILED DESCRIPTION

Specific structural or functional descriptions of exemplary embodimentsof the present disclosure disclosed in this specification or applicationare exemplified only for the purpose of explaining the exemplaryembodiments according to the present disclosure, the exemplaryembodiments according to the present disclosure may be carried out invarious forms, and it should not be interpreted that the presentdisclosure is limited to the exemplary embodiments described in thisspecification or application.

Because the exemplary embodiments according to the present disclosuremay be variously changed and may have various forms, specific exemplaryembodiments will be illustrated in the drawings and described in detailin the present specification or application. However, the descriptionsof the specific exemplary embodiments are not intended to limitexemplary embodiments according to the concept of the present disclosureto the specific exemplary embodiments, but it should be understood thatthe present disclosure covers all modifications, equivalents andalternatives falling within the spirit and technical scope of thepresent disclosure.

The terms such as “first” and/or “second” may be used to describevarious constituent elements, but these constituent elements should notbe limited by these terms. These terms are used only for the purpose ofdistinguishing one constituent element from other constituent elements.For example, without departing from the scope according to the conceptof the present disclosure, the first constituent element may be referredto as the second constituent element, and similarly, the secondconstituent element may also be referred to as the first constituentelement.

When one constituent element is described as being “coupled” or“connected” to another constituent element, it should be understood thatone constituent element can be coupled or connected directly to anotherconstituent element, and an intervening constituent element can also bepresent between the constituent elements. When one constituent elementis described as being “coupled directly to” or “connected directly to”another constituent element, it should be understood that no interveningconstituent element is present between the constituent elements. Otherexpressions, that is, “between” and “just between” or “adjacent to” and“directly adjacent to”, for explaining a relationship betweenconstituent elements, should be interpreted in a similar manner.

The terms used in the present specification are used to just describe aspecific embodiment and do not intend to limit the present disclosure.Singular expressions include plural expressions unless clearly describedas different meanings in the context. In the present specification, itshould be understood the terms “comprises,” “comprising,” “includes,”“including,” “containing,” “has,” “having” or other variations thereofare inclusive and therefore specify the presence of stated features,numbers, steps, operations, elements, components, or combinationsthereof, but do not preclude the presence or addition of one or moreother features, numbers, steps, operations, elements, components, orcombinations thereof.

Unless otherwise defined, all terms used herein, including technical orscientific terms, have the same meaning as commonly understood by thoseskilled in the art to which the present disclosure pertains. The termssuch as those defined in a commonly used dictionary should beinterpreted as having meanings consistent with meanings in the contextof related technologies and should not be interpreted as ideal orexcessively formal meanings unless explicitly defined in the presentspecification.

Hereinafter, an exemplary embodiment of the present disclosure will bedescribed in detail with reference to the accompanying drawings. Likereference numerals indicated in the respective drawings refer to likemembers.

Referring to FIGS. 1 to 6 , an embodiment of a reducer for an electricvehicle according to the present disclosure includes: an input shaft INconnected to a motor MG, a differential DF disposed coaxially with theinput shaft IN and installed to be relatively rotatable, a planetarygear train PG configured to decelerate power of the input shaft IN andtransmit the power to a differential casing DC of the differential DF,and a drive shaft DS configured to penetrate the input shaft IN andcoupled to one side gear SG of the differential DF.

That is, according to the present disclosure, when the power of themotor MG is inputted through the input shaft IN, the planetary geartrain reduces the speed and then outputs the power to the differentialDF. One of the two drive shafts DS, which transmit power to two drivingwheels from the differential DF, penetrates the input shaft IN asdescribed above.

The planetary gear train includes a sun gear S disposed on the inputshaft IN, a carrier C engaging with the differential casing DC, and aring gear R fixed to a casing CS.

That is, the power inputted to the sun gear S from the input shaft IN isdecelerated by the carrier C and transmitted to the differential casingDC.

Planetary pinions rotatably supported on the carrier C includes a firststage pinion PN1 engaging with the sun gear, and a second stage pinionPN2 engaging with the ring gear R. The first stage pinion PN1 may have alarger diameter than the second stage pinion PN2.

Therefore, the planetary gear train implements a reduction ratiodetermined by a ratio of number of teeth between the first stage pinionPN1 and the second stage pinion PN2 in addition to a reduction ratiodetermined by the number of teeth of the sun gear S and the ring gear R.Therefore, the number of components and weight required to configure theplanetary gear train PG may be reduced, and a relatively high reductionratio may be implemented.

The carrier C and the differential casing DC may engage with each otherthrough a spline coupled to be slidable in an axial direction.

Therefore, the differential DF may be easily assembled with the carrierC of the planetary gear train PG only by sliding in the axial direction,and the differential DF may also be easily disassembled, therebyensuring improved assembly properties and maintainability.

In addition, according to the configuration modularized to easily coupleand disassemble the planetary gear train PG and the differential DF, anadditional planetary gear train, instead of the differential DF, may beeasily assembled with the carrier C, such that the configuration may beeasily modified to increase a gear ratio of the reducer.

For reference, the term ‘axial direction’ may be understood as meaningan axial direction of the input shaft IN.

An end of the input shaft IN is inserted into the differential casingDC. A first bearing B1 is installed between an inner circumferentialsurface of the differential casing DC and an outer circumferentialsurface of the input shaft IN.

The input shaft IN is supported by a second bearing B2 and a thirdbearing B3 disposed to be spaced apart from each other in the axialdirection of the casing CS. The differential casing DC is supported onthe casing CS by a fourth bearing B4 at a position spaced apart from thefirst bearing B1 in the axial direction.

Therefore, the input shaft IN is stably and rotatably supported on thecasing CS by the second bearing B2 and the third bearing B3. Thedifferential casing DC is stably and rotatably supported by the firstbearing B1 and the fourth bearing B4.

That is, one side of the differential casing DC is supported on thecasing CS by the fourth bearing B4, and the other side of thedifferential casing DC is supported on the casing CS by the firstbearing B1 through the input shaft IN. Therefore, a separate bearing forsupporting the other side of the differential casing DC directly on thecasing CS need not be provided, and an intermediate wall or the likeneed not be provided on the casing CS to mount the bearing. Therefore,it is possible to reduce the overall length and weight of the reducer.

In addition, in the present embodiment, as illustrated in FIG. 1 , thecarrier C of the planetary gear train PG is positioned to overlap theinput shaft IN, the first bearing B1, and the differential casing DC anddisposed at the position at which the input shaft IN, the first bearingB1, and the differential casing DC overlap in the radial direction. As aresult, it is possible to reduce the overall length of the reducer.

Meanwhile, in the second embodiment illustrated in FIG. 3 , a parkinggear PK is provided on the carrier C, and the other components arealmost identical to those in the first embodiment.

For example, as illustrated in FIG. 3 , the parking gear PK may beassembled with the carrier C.

That is, a spline is formed between an outer circumferential surface ofthe carrier and an inner circumferential surface of the parking gear PKso that the parking gear PK may be coupled by sliding in the axialdirection on the outer circumferential surface of the carrier C. Theparking gear PK is inserted into the carrier C using the spline and thenfixed by a snap ring SR or the like.

For reference, unlike FIG. 1 , the carrier C extends toward thedifferential DF to install the parking gear PK at the portion where theparking gear PK is installed, but the other components illustrated inFIG. 3 are identical to those illustrated in FIG. 1 .

Therefore, since the overall length of the reducer for installing theparking gear PK is not separately increased, the configuration above mayultimately reduce the overall length of the reducer.

A pin insertion port 1 for fixing a pinion shaft PS is formed in thedifferential casing DC and opened toward the carrier C of the planetarygear train PG.

Therefore, in a state in which a fixing pin 3 for fixing the pinionshaft PS is inserted into the pin insertion port 1, the carrier C ispositioned outside the fixing pin 3, thereby preventing the fixing pin 3from being completely separated from the differential casing DC. Thedifferential casing DC and the carrier C have the same rotational speedeven though the fixing pin 3 is in contact with the carrier C.Therefore, damage to the fixing pin 3 and the differential casing DC isprevented.

An oil supply part 5 is provided in the casing CS to supply oil througha space between the input shaft IN and the drive shaft DS. The oilsupply part 5 is formed to supply the oil to a gap between the end ofthe input shaft IN and the drive shaft DS.

Therefore, the oil pumped to the oil supply part 5 by an oil pump or thelike may lubricate the third bearing B3 at the position adjacent to theoil supply part 5 and also effectively lubricate the first bearing B1 byflowing along the gap between the input shaft IN and the drive shaft DS.

In addition, an oil hole is additionally formed in the input shaft IN,such that the oil for lubricating the second bearing B2 may be suppliedfrom the gap between the input shaft IN and the drive shaft DS. Further,the oil required to lubricate a fifth bearing B5 for supporting thecarrier on the casing CS in FIG. 1 may be supplied by a method like themethod of lubricating the second bearing B2.

Meanwhile, in the third embodiment illustrated in FIG. 4 , the parkinggear PK is installed on the differential casing DC, and the othercomponents are almost identical to those in the first embodiment.

In addition, in the fourth embodiment illustrated in FIG. 5 , adisconnector DN is slidably provided in the differential casing DC toengage or disengage the differential casing DC and the carrier C, andthe other components are almost identical to those in the firstembodiment.

When the vehicle operates with the motor MG, the disconnector DNmaintains the connected state to transmit the power from the motor MG tothe differential DF. However, when the vehicle coasts, the disconnectorDN may disconnect the differential DF and the motor MG to allow thevehicle to continue to coast for a long period of time in a state inwhich inertia resistance caused by the motor MG is excluded. As aresult, it is possible to improve the efficiency of the vehicle.

In addition, in the fifth embodiment illustrated in FIG. 6 , both theparking gear PK and the disconnector DN are installed in thedifferential casing DC.

While the specific embodiments of the present disclosure have beenillustrated and described, it will be obvious to those skilled in theart that the present disclosure may be variously modified and changedwithout departing from the technical spirit of the present disclosuredefined in the appended claims.

The invention claimed is:
 1. A reducer for an electric vehicle, thereducer comprising: an input shaft connected to a motor; a differentialdisposed coaxially with the input shaft and being rotatable relative tothe input shaft; a planetary gear train configured to decelerate powerof the input shaft, and to transmit the power to a differential casingof the differential; and a drive shaft coupled to one side gear of thedifferential, wherein the drive shaft is configured to penetrate theinput shaft; wherein an end of the input shaft is inserted into thedifferential casing, and a first bearing is installed between an innercircumferential surface of the differential casing and an outercircumferential surface of the input shaft.
 2. The reducer of claim 1,wherein the planetary gear train comprises: a sun gear provided on theinput shaft; a carrier engaging with the differential casing; and a ringgear fixed to a casing.
 3. The reducer of claim 2, wherein planetarypinions rotatably supported on the carrier comprise: a first stagepinion engaging with the sun gear; and a second stage pinion engagingwith the ring gear; wherein the first stage pinion has a larger diameterthan the second stage pinion.
 4. The reducer of claim 2, wherein thecarrier and the differential casing engage with each other by a splineby sliding in an axial direction.
 5. The reducer of claim 2, wherein aparking gear is positioned on the carrier.
 6. The reducer of claim 5,wherein a spline is formed between an outer circumferential surface ofthe carrier and an inner circumferential surface of the parking gear sothat the parking gear is coupled to the outer circumferential surface ofthe carrier by sliding in an axial direction.
 7. The reducer of claim 2,wherein a pin insertion port for fixing a pinion shaft is positioned inthe differential casing and opened toward the carrier of the planetarygear train.
 8. The reducer of claim 1 wherein the input shaft issupported on the casing by a second bearing and a third bearing, thesecond bearing and the third bearing being spaced apart from each otherin an axial direction, and the differential casing is supported by afourth bearing on the casing at a position spaced apart from the firstbearing in the axial direction.
 9. The reducer of claim 8, wherein anoil supply part is positioned in the casing to supply oil through aspace between the input shaft and the drive shaft, and the oil supplypart is configured to supply the oil to a gap between the end of theinput shaft and the drive shaft.